Transmission control system



1949- R. LAPSLEY TRANSMISSION CONTROL SYSTEM Filed Aug. 10, 1945 2Sheets-Sheet 1 llllll.

w m MY i R?lllllllllllllllllllllllllllIIHIHIIIIIIIIIIIHIIIHIIllllllllllllllllllllllmfllllFeb. 8, 1949. R. LAP SLEY TRANSMISSION CONTROL SYSTEM 2 Sheets-Sheet 2Filed Aug. 10, 1945 Fatented Feb. 8, 1949 TRANSMISSION CONTROL SYSTEMRobert Lapsley, Berrien Springs, Micln, assignor to Clark EquipmentCompany, Mich., a corporation of Michigan Buchanan,

Application August'lii, 1945, Serial No. 610,037

13 Claims. 1

This invention relates to transmission controlsystems, and moreparticularly is concerned with a control system for a transmissionhaving a fluid torque converter in combination with a plurality of geartrains for providing varying speed ratios.

More particularly the present invention relates to the fluid controlsystem whereby operation and selection of the various gear trains isprovided in conjunction with a new and novel provision for developingthe fluid pressure and control of the application of this fluid pressurethrough the selecting control valve.

While the control system is shown and described in conjunction with atransmission of the type utilizing a torque converter with two or moregear trains in which the gears are selectively coupled for drivingoperation through fluid operated clutch mechanism, it is to beunderstood that the system itself is capable of use in other types oftransmission designs, and is described in connection with the presenttransmission construction only for the sake of illustration.

In a transmission of this general type it is necessary to provide afluid pressure reservoir so that when a particular fluid clutch is to beactuated, the fluid under pressure is'immediately available foractuation of the clutch. At the same time it is also necessary toprovide for some shock 'absorbing means to eliminate the possibility ofthe clutch engaging so quickly as to produce a shock in the transmissionand thus provide an objectionable operation. At the same time it isnecessary that the system be so designed as to be used in con unctionwith the fluid system of the torque converter for purposes of simplicityand economy.

One of the primary features of the present invention is a provision ofan accumulator or metering device so arranged as to provide for buildingup of fluid pressure to accelerate the engagement of the clutches whichare actuated by fluid pressure and which also acts partly as a shockabsorber to prevent unnecessary shock loads in the clutches. In additionto this shock absorber, means is provided in which the pressure of thefluid pressure developing source is built up, which shock absorber actsas a dumping means for automatically dumping a certain amount of fluidor oil into the lubricating portion of the system to prevent the undueshock loads which might otherwise occur.

Another feature of the present inventionis the provision of a two-stagepumping arrangement to provide at low speed, such as idling, asuflicient volume of oil for the control system so that in addition tothe leakage through the control mech- (cn. 11-364) f anism and therequirements for lubrication, there will be a volume of oil such that aslight pressure will be built up whereby even at idling the controlmechanism can be operated, since there is no running torque to overcomeat this time. However, upon acceleration of the engine from idlingposition, the pump system is so arranged as to change from a parallelarrangement, which provides the greater volume of oil, to a seriesarrangement, which provides for increased pressure necessary to operateclutch mechanisms when considerable torque must be handled duringshifting from one speed ratio to another. This pump system is automaticin operation, being so arranged as to shift from parallel operation toseries operation when the pressure reaches approximately 55% of themaximum pressure which can be deervoir of fluid under pressure and to ashock absorber which provides for cushioning the shock of engagement ofthe clutches by dumping a certain volume of oil, this oil so dumpedbeing added to the lubricating system so that at the moment the clutchesare energized to engagement, a. greater amount of lubricating oil issupplied thereto momentarily which provides for proper lubrication underthe conditions of high stress that occur during clutching engagement.

Still another feature of the present arrangement resides in theprovision of an initial stage of fluid pressure development whichdevelops a certain fluid pressure for use in transmitting oil to thetorque converter. this oil being transmitted to the converter only whensuflicient pressure is developed, such as when the engine is acceleratedbeyond idling position that loading of the converter with oil isdesired. In the meantime, and during the time that the engine is idling,a predetermined amount of the oil pumped through the initial pump isallowed to flow into the transmission system for lubricating purposes,thus providing for adequate lubrication of the transmission during alltimes that the engine is running and, with the features mentioned above,providing for additional lubrication in the transmission when theclutches are actuated.

It is, to be pointed out that with thepresent system one advantage whichis attainedis that) the entire system is automatic in operation, re-

quiring no control on the part of the operator due variousfiuid lineswhich automatlcally'operate to distribute the fluid in the propermannerand to provide for building upofadequate pressure whensuch'pressure isnecessary for operation of common point in thetransmission system.

. I Other objects and advantages of the present invention will appearmore fully from the following detail description which, taken inconjunction with theaccompanying drawingswill dis- Referring now firstto Figure 1, i this drawingthere is described a transmission assemblycomtothe'provision of pressure control valves in the I the selectiveclutches. Furthermore, the system is very compact, since all thepumpsmay be arranged on a common shaft and driven from a prising a bellhousing 5 within which is mounted I a known conventional torqueconverter 6, and which converter, if desired, may be of the typedisclosed in my copending application, Serial No. 526,829, filed March-15, 1944, This torque converter has its impelleror pump element adaptedto be driven from the flywheel I: connected. to

flywheel housing 8 into which the larger and of earfmemb'er' 29 havingThe transmission iisfprevidee with a. counter.

'- shim 25 upon which is mounted the-gear element 21' having mesh gengagemcntwith the gear 23 and splined to the countershaft 2S. Alsomounted on thecountershaft 28. andseparated from the gear ine pa r 12asamtecebie v nt m sh ng enagementwlth the ge'arzs v It'zwillbenoted-{tha'tone of the side' plates '22 or the gear 23 is providedwithan internal clutch tooth portion 30 having me'shing engagement with'a-corresponuding clutch portion; 32 of the driving shaft .9 extendinginto the transmission. Thus, it will-be seen that the gear 231sconstantly driven and, in turn, constantly drives the gear 21 on thecountershaftlwhich produces rotation of the countershaft. Whena gearreduction is desired in the transmissiomthe pistons 20 of. hub

member l8 are actuated, thereby clutching gear 25 to shaft l5 and, withthe clutch member 33 engaged with the gear 29, this gear is clutched tothe countershaft and consequently gear 29 drives gear 25 at a reducedspeed. When it is desired to shift to direct drive, the fluid pressureagainst piston 20 is released ,and iiuid under pressure is introducedbetween pistons l9, thereby clutching gear 23 directly to shaft Hi andproviding a direct drive from shaft 9 through shaft IE to the propellershaft of the vehicle.

It is obvious, of course, that additional gear reductions may beprovided in which additional piston clutch mechanism such, for example,as

illustrated diagrammatically in Figure 2 must be provided in each eartrain.

with the present transmission, reverse drive is produced by shaft 9driving gear 23 which, in turn, drives gear 2]. This, in turn, with theclutch gear33 shifted to the right to engage with I the engine crankshaftan'd housed withinthe the bell housing is piloted in the usualmanner.

The output shaft of the transmission, indicated generally at ;9, hasconnection: as is'known with the rotor or driven element of the torquecon- The shaft 9 extends through the bell housing 5 into thetransmission housing l3, which housing is provided with a cover plate llcarrying on its under surface a selector or control valve housing l5enclosing suitable valve mechanism for effecting shifting of thetransmission and which mechanism may if desired be similar to thatdisclosed in the aforementioned copending application.

Within the transmission housing I3 is mounted a transmission outputshaft I 6, which shaft has secured thereon as by splines or the like,two hub members l1 and I8. The hub members I! and I8 are adapted tocarry respective circumferentially arranged series of opposed pistons I9 and 20 which, when energized by fluid under pressure, operate toengage in suitable grooves carried in side plates 22 of an externalannular gear element 23 surrounding the hub member I] and in side plates24 of a gear element 25 surrounding the hub member Ill. The details of,operation of these pistons is disclosed in the aforementioned copendingapplication.

the-reverse idler 34, drives the reverse idler which has the portion 35thereof in meshing engagement with the ear 29 tothereby drive gear 29.This, in turn, drives gear-25 in a reverse direction and actuation ofthe piston clutches 20 in the hub member-18 clutches gear 25 to shaft I6I referred to or may be of the type shown in application of Burton L.Mills, Serial No. 548,741 filed August 9, 1944, now Patent No. 2,419,906issued April 29, 1947.

While only two fluid conduits 31 and 38 are shown, one for each ofthehub clutches H and It in the transmission of Figure 1, it will beobserved that with the additional piston clutches for the additionalgear trains of Figure 2 additional passageways 92 and 83 are provided.

Fluid under pressure is adapted to be admitted by actuation of theselector valve l5 into passageway 38 which extends to passageway 38' ofdistributor 39. A passageway 38" extends from passageway 38f to apassageway 42 extending axially within output shaft i6 and which latterpassageway is connected by a port for actuating fluid pistons IS. Theselector valve 15 is further operable to selectively admit fluid underpressure to passageway 31 whichextends to and has communication withpassageway 31' of distributor 39. The passageway 31' has connection bymeans of a suitable passageway (not shown) with the passageway 88extending axially within output shaft l5 and which latter passageway isconnected by a port ll for actuating fluid pistons 28. A preferred formof distributor cons'truc tion for effecting the selective delivery offluid under pressure to actuate fluid pressure responsive clutches suchas that shown at I9 and 28 is disclosed in my above referred tocopending application to which reference may be had.

Considering now the fluid control system for controlling the operationof the piston clutches and providing the desired actuation thereof underfluid pressure, reference is made to Figure 2. As has been previouslystated, the gear ll of shaft I2 is driven from the drive member of thetorque converter and consequently is driven at all times that the engineis in operation. Mounted upon the shaft I2 adjacent the gear II is a.primary pump, indicated diagrammatically at 59, having an inlet 52 andan outlet 53. The pump 58 may be of the gear rotor type and ispreferably a large volume low pressure pump which draws oil from astorage tank or reservoir and delivers it under pressure through theoutlet 53 into a control valve indicated generally at 54. However, aportion of the oil delivered by the pump 50 passes through thepassageway 55 and through a restricted orifice 55 into a conduit 51leading to a lubricating system to the transmission which will bedescribed in detail hereinafter.

The control valve 55 includes a sliding plunger 58 which, at one end, isenlarged to receive therepressure is reached, the plunger 58 is shifted"to the left, by pressure acting against end 6| idling position, thepressure developed by the line 15 to line 18 leading out from the outlet19 of the control valve. This valve also is controlled by predeterminedspring pressure which is preferably adjusted so that it operates to openthe connection between lines 15 and 18 when the pressure reachesapproximately 55% of the ultimate servo pump pressure. When this occurs,the fluid from line 11 operates through a line 80 to close check valve61, thereby forcing all of the fluid delivered into line 63 from pumpinto the first stage pump 65. This oil is then discharged from pump 65through outlet 85, line 15 and line 18 to inlet 58' of the second stagepump 69. From this point the oil under pressure is discharged throughoutlet I8, into line 12, a back pressure line 82 assuring closing ofcheck valve 13 to prevent pump 65 discharging into line H. Thus, the twopumps and 69 shift from parallel operation to series operation when apredetermined pressure is reached, thereby produc-' ing higher pressurebut smaller volume delivery of oil through line 12 and thence to theselector control system. When the engine is idling, howwhich is ofslightly less diameter of the cylinder in which the plunger operates toadmit fluid under pressure therebehind, against the pressure of spring59 and the fluid under pressure from outlet 53 passes around the reducedstem 60 of the plunger into the outlet passageway 62 and from thispassageway is delivered into the torque converter, there preferablybeing a. cooling interchanger interposed between the torque converterand the reservoir or supply tank to remove the heat generated by theconverter and to assure a supply of cool oil to the primary pump 50. Arelief outlet 62' provides for returning. fluid leaking past plunger 58to the sump or otherwise, as desired.

In addition to the volume of oil necessary to operate the converter, aportion of the oil delivered by the pump 50 passes from'the conduit 55through the conduit 53 to the line 54. Here again the oil is divided, aportion of it passing from line 54 into the inlet of the first stage ofa servo pump assembly, indicated generally at 55, the

outlet of this pump being indicated at 65, an-

other portion of the oil entering into the conduit 54, passing throughcheck valve 81 and into the inlet 58 of the second stage servo pump 69from which it is delivered through outlet 18 to a com mon pressure fluidline 12 which also receives oil under pressure from outlet 56 of thepump 65, past check valve 13 and through line H. When the. engine isidling, the fluid pressure of the servo pump mechanism indicated at andpassing from outlet 65 to line 15 is not sufllcient to actuate thecontrol valve indicated generally at 15. However, when the engine isaccelerated beyond ever, and the control valve 16 is in the positionshown, the pumps operate in parallel, thereby producing a larger volumeof-oil but under less pressure. operation is produced automatically inance with the pressure developed.

Preferably, the outlet of pump 68 is so arranged as to provide asecondary discharge line 83 which leads to the high pressure controlvalve 84 which is so designed that when the pressure of the two pumpsunder high speed of the engine exceeds a predetermined maximum, thevalve 84 will act as a relief valve to open the passageway from line 83to discharge line 85, thereby relieving any excessive pressure developedwhen the pumps are operating in series.

From the line 12 oil under pressure is delivered tothe point '86, aportion of this oil passing through line 81 into the control valve l5,the line 81 corresponding to the passageway 35 of Figure 1. However, anadditional portion of the oil under pressure from line 12 passes throughline 88 into the accumulator 89, which accumulator acts as a reservoirto store oil under pressure, thereby providing a sufficient volume ofoil under pressure such that when one of the control selections is madein the valve l5, this oil will act to speed up engagement of theselected clutch mechanism and will also act as a cushioning charged withfluid under pressure the other of the passageways are under bleed.Valves of this type are well known in the art and it is believed neednot be further described for an understanding of my present invention.The dotted line indicated at 90 shows the return flow of oil underpressure from the outlet 89 into the selector valve l5 when the valve isactuated to provide for flow of oil pressure through one of the selectedclutch control passageways 31, 38, 92 or 93. The passageways 31 and 38correspond to those shown inFigure 1 and are arranged to provide' Thechange from parallel to series accordthe pump 59.

. 7 for selective actuation of clutch I9 or 20' or clutches 92' or 99depending upon the selective actuation of the control mechanism withinthe valve l.

The line 98 leading from the high pressure oil line 12 also leadsthrough line 94 to the inlet port 95 of a dump valve mechanism generallyindicated at 96, associated with a shock absorber diagrammatically-shownat 91. The shock absorber 91 is so designed as to provide an initialcollapsible bladder 99 subject to pressure from an air pressure line 99or controlled by spring pressure if so desired. This pressure line 99also acts as the controlling factor for controlling pressure on theaccumulator 99} which also has a collapsible bladder 9I therein. Asuitable check valve is interposed in the upper end or the members I9and 91, as indicated at I90, to provide for maintaining a predeterminedpressure with the collapsible bladder against which the oil underpressure must react.

The dump valve 99 consists of a sliding plunger which is providedadjacent its lower end with a series of radial ports I92 and with a webportion I93 which acts as a piston member so that the oil under pressurefrom line 12 operates against the web I09 to force the plunger 99upwardly, thereby opening ports I92 into the annular chamber I fromwhence the oil may pass around the web I09 and back into the radialports III! thereabove and thence through the interior of ,the sleeve 99into the interior of the shock absorber 91. It will be noted that whenthe plunger has moved upwardly in response to pressure from line I2, theupper series of radial ports I99 are closed so that the oil underpressure enters into the chamber 91. and acts against the collapsiblemember 99 to provide for storing this oil under pressure within theshock absorber.

When the pressure from line 12 is directed into the control valve I5 dueto actuation of the valve for energizing one Of the clutches, thepressure drops against the web I03 of the dump valve 99 and the pressureof the oil within the shock absorber 91, due to the action of thenormally to only partially discharge oil collected therein whereas thedischarge from the shock absorber is substantially complete so that thelatter primarily eflects the cushioning engagement of the clutches.

In the operation of the construction and the system as described whenthe engine is idling, the torque converter 6 is rotating at arespectively slow speed. Consequently, the shaft I2 driven from gears I9and II is also rotating at a relatively slow speed. Y

Consequently, the large volume low pressure primary pump 59 isdelivering a large quantity of oil under'low pressure to the controlvalve 94 and also through the metering restriction 96 and lubricationline 51 to the transmission. In addition, a small portion of this oil isbeing delivered to the first and second stage pumps 95 and 69 which, inturn, are at this time arranged for parallel operation and consequentlyprovide for delivery 01. a relatively large volume of oil at lowpressure to the control valve I5 and to the accumulator 89 and shockabsorber 91.

The volume of oil delivered to the line 12 at this time is such as toprovide for taking care of all-1eakage in the system, for the properamount of lubrication through line 91, and for buildin up some pressurewithin the accumulator 89 and shock absorber 91. This pressure issuillcient so that if the control valve I5 is operated, the selectedclutch can be engaged, since at this time there is relatively notorqueto be handled by the clutch and it. will be v capable of operation.

expandable member 99, forces this oil outwardly.

the shock absorber 91 into the lubrication line 91 which leads into thetransmission for lubricating the bearings upon which the gear members,such as gears 23 and 29, are mounted. Thus, simultaneous with theenergization of one or the clutches within the transmission a dumpaction oil-the lubrication oil under pressure is provided from the shockabsorber 91, assuring-increased lubrication of the clutches at the time'that they are under the most severe stress. This is a very desirablefeature, since it augments the normal lubrication provided from Further,upon the shock absorber 98 operating to dump its charge of oil into thelubricating system it, in effect, creates a void in the pressure linewhich is eiiective to prevent overloading of the selected clutch byfluid under pressure delivered thereto by the accumulator 99 and fromthe pressure line I2. As above related upon clumping ofthe oil fromshock absorber 99 into the lubricating line 51 the fluid under pres- Assoon as the engine is accelerated from idling position, however, thelarge volume pump 99 operates to produce sufilcient pressure to actuaterelief valve 58, thereby forcing oil into the converter for producingdriving torque and at the same time forces oil under sufllcient pressureinto the line 64 to insure proper delivery ofoil through the pumps 95and 69 to start building up an outlet pressure in the accumulator 99 andshock absorber 91. As the engine continues to accelerate. the pressuredeveloped by the pump 65 is sufiicient to actuate relief valve l1,thereby changing the pumps from parallel operation to series operation,producing a higher pressure but a smaller volume of oil throughdischarge outlet III into the line I2 to produce an increased amount ofpressure in the accumulator 99 and in the shock aband load on thevehicle are such as to cause actuation of another one of the clutchescontrolled by the control mechanism within valve I5, the oil underpressure in the accumulator 99 returns through line 99 into the controlvalve to augment the relatively small supply of high pressure oil beingintroduced into line 12 to insure rapid engagement of the selectedclutch. However, the dump valve in the shock absorber 91 also functionsat this time due to reduction of pressure of one of thecontrol lines 91,I9, 92 or 99 to dump a sufllcient volume of oil out of the shockabsorber into the lubricating system as above described. As this clutchengages and the oil line thereto becomes filled with oil under pressureto maintain clutch engagement, the delivery of oil from line 12 againbuilds up a fluid head in the accumulator 89 and in the shock absorber91, thereby conditioning the system for proper rapid but cushionedengagement of any other selected clutch as the selector valve I is againoperated.

It is therefore believed apparent that with the present control systemthere is provided means for assuring an adequate volume of high pressureoil to speed up the engagement of the clutch mechanism by rapidlyfilling up the space caused by piston displacement and insuring pressurein the oil introduced therein, while the shock absorber 91 at the sametime provides a cushioning action due to the divided flow of oil underpressure from the accumulator to prevent too rapid an operation whichmight result in grabbing of these clutches or damaging thereof by fluidunder pressure in an amount in excess of that required to effectsatisfactory operation of the clutches.

It is, of course, apparent that individual shock absorbers such asdiagrammatically indicated at H2, l l 3 and H4 can be used with each ofclutches I9, 20' and 92' which in this arrangement the shock absorber'98 serves the clutch 93 which, if in the engagement of the severalclutches the variation in volume of oil required for actuation of theseveral clutches is so great that a common shock absorber cannot beused. In this arrangement the shock absorbers H2, H3 and III aredisposed between selector valve l5 and their respective clutches and aresuitably proportioned to provide for the volume of oil required to behandled by each thereof in the engagement of the clutches with whichthey are associated. It should also be noted that the oil from the shockabsorber 98 is added to the lubrication oil at the moment of applicationof pressure to one of the clutches, thereby giving an increased oil flowat the moment of clutch engagement to provide in creased lubrication atthe time of more severe usage. In the actual construction'of atransmission, provision is made for assuring that each clutch willreceive its share of the lubricating oil. In other words, the clutchconstruction so far 'as the lubricating ports are co; erned, is meteredfor proper lubrication of each clutch.

It is therefore believed that the present system provides 'a novel typeof control for a fluid operated transmission of the type disclosed, andwhile variations may be made in certain details of this construction. Ido not intend to be limited except as defined by the scope and spirit ofthe appended claims.

Iclaim:

1. A fluid pressure control system for a fluid drive transmission havinga plurality of fluid pressure operated clutches for selecting variousspeed ratios, and a selector valve for selectively controlling theoperation of said clutches, comprising pump means operating to deliverfluid under pressure to said selector valve, an accumulator in saidsystem for storing fluid under pressure, and a shock absorber foraccumulating fluid under pressure, said accumulator bein connected tosaid selector valve for providing a large volume of high pressure fluidupon actuation of said valve to speed up engagement of the selectedclutch, and said shock absorber having means for dumping a volume ofhigh pressure fluid into said transmission to reduce the pressure in theshock absorber for cushioning the engagement of said selected clutch bythe high pressure fluid admitted to the latter, and to provideadditional lubrica-' tion as said selected clutch is actuated.

2. A fluid pressure control system for a transmission providingsior aplurality. of gear ratios, pressure-operated clutch means for eachratio, a source of fluid under pressure, and a selector valve fordirecting said fluid to one of said clutches comprising accumulatormeans providing a reservoir of fluid under pressure to said selectorvalve for speeding up operation of said clutch means, and shock absorbermeans in said pressure source for dumping fluid under pressure when saidselector valve is actuated.

3. A fluid pressure control system for a transmission having a pluralityof gear ratios, fluid pressure-operated clutches for selectivelyengaging each ratio, a torque converter for delivering torque to saidtransmission from an engine, and a valve for selectively directing fluidunder pressure to said clutches comprising a primary low pressure highvolume pump adapted to be driven by said engine, a pair of secondaryhigh pressure low volume pumps receiving fluid from said primary pumpand arranged to operate in parallel when said engine is idling butincluding automatic pressure-responsive valve means for changing saidsecondary pumps to series operation when said engine accelerates beyonda predetermined point, and means including an accumulator for deliveringhigh pressure fluid to said selecting valve.

4. The pressure control system of claim 3 including pressure responsivevalve means for delivering a portion of the fluid output of said primarypump to said converter when said engine exceeds idling speed.

5. The pressure control system of claim 3 including a pressurecontrolled shock absorbing chamber in parallel with said accumulator fordumping high pressure fluid into said transmission for lubricatingpurposes upon actuation of said selecting valve.

6. A fluid control system for an assembly including a torque converterdriven from a power source, a change speed transmission driven by saidconverter and having a plurality of gear trains therein, fluidpressure-operated clutches for connecting and disconnecting said geartrains, and a selector valve for directing fluid under pressureselectively to said clutches comprising a fluid lubrication system forsaid transmission, and a fluid pressure supply system for said selectorvalve, said fluid pressure supply system including a primary pumpdelivering a portion of its output to said lubrication system, meansresponsive to operation of said pump above idling speed of said powersource for delivering fluid to said converter, and a pair of secondarypumps receiving the balance of the output of said primary pump andarranged for automatic change over from parallel operation at idlingspeed to series operation at a predetermined point above idling speed todeliver high pressure fluid to said selector valve.

7. The fluid control system of claim 6 characterized by the fluidpressure supply system thereof including an accumulator in parallel withsaid selector valve and operable to augment the fluid flow from saidsecondary pumps when said selector valve is actuated for acceleratingthe operation of the selected clutch.

8. The fluid control system of claim 6 characterized by the fluidpressure supply system thereof including parallell y connectedaccumulator and shock absorber inthe delivery line to said selectorvalve, said accumulator storing fluid under high pressure foraccelerating the operation of a the selected clutch and said shockabsorber providing a dumping action of high pressure fluid into thetransmission to reduce the pressur in said shock absorber for cushioningclutch operation by high pressure fluid in the fluid pressure supplysystem.

9. The fluid control system of claim 6 charac-. terized by the fluidpressure supply system thereof including accumulator means connected tothe high pressure side of said secondary pumps and having anfegrpansiblechamber subject to entry of high pressure fluid providingior augumentingthe volume or high pressure fluid flowing through said selector valvewhen actuated to operate one of said clutches.

10. Thefluid control system or claim 8 eharacterlzed by the fluidpressure supp y system thereof including shock absorbing means connectedto the high pressure side of said secondary pumps and having anexpansible chamber subject to entry of high pressure fluid and includingvalve means responsive to drop in pressure caused by through said gearmeans, and a common control a valve for selectively directing highpressure fluid to the clutches comprising, a fluid pressure develcplngsystem having its high pressure side connected to said valve, and anaccumulator adapted to be connected in parallel with said valve havingan expansible chamber providing for storage of high pressure fluidagainst a predetermined pressure in said fluid pressure developingsystem whereby upon actuation of said valve said accumulator fluidaugments the volume of hi h pressure fluid flowing from the valve to theselected clutch to accelerate its operation.

12. The fluid control system of claim 11 including a shock absorbersimilar to said accumulator but arranged to dump its fluid into the gearmeans for lubrication purposes when said valve i actuated.

13. The fluid control system oi claim 11 wherein said pressuredeveloping system includes a primary pump of the low pressure highvolume delivery type, a pair or secondary pumps arranged for paralleloperation and connected to the discharge side of said primarypump, andpressure responsive valve means for changing said secondary pumps toseries operation when the discharge pressure of one of said pumpsreaches a predetermined amount.

- ROBERT LAPSLEY.

REFERENCES crrnn The following references are of record in-the file ofthis patent:

UNITED STATES PATENTS Number

